Rotary electric machine

ABSTRACT

In a vehicular alternator, a stator is arranged to oppose a rotor in a housing. The stator includes a stator core, which forms a plurality of slots extending in an axial direction of the stator core, and a stator winding wound around the stator core. The stator winding includes electric conductors held in the slots. Each of the electric conductors has a circumferential width that is smaller than a circumferential distance between a first wall and a second wall defining the slot. The first wall and the second wall oppose each other in a circumferential direction. The electric conductors are alternately in contact with one of the first wall and the second wall.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2002-202073filed on Jul. 11, 2002, the disclosure of which is incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to a rotary electric machine such as avehicular alternator mounted on passenger vehicles or trucks.

BACKGROUND OF THE INVENTION

In a vehicular alternator disclosed in JP-B2-2927288 (U.S. Pat. No.5,998,903), a winding of a stator is constructed of a plurality ofU-shaped conductor segments. The U-shaped conductor segments areinserted in slots of a stator core from an axial end of the stator core.Ends of the U-shaped conductor segments are connected at an oppositeaxial end of the stator core.

In this kind of stator core, small gaps are required between theconductor segments and inside walls defining the slots to reduceresistance therebetween at the time of installation of the conductorsegments. However, if the conductor segments are arranged in the slotswithout any limitations, the conductor segments are less likely to makecontact with the inside walls, or likely to lean against and contactonly one side of the inside walls.

In the case that the conductor segments do not make contact with theinside walls of the slots, efficiency of heat transfer from theconductor segments to the stator core decreases, so temperature of theconductor segments increases. As a result, it is likely that poweroutput will decrease. On the contrary, in the case that the conductorsegments lean to one side and contact only one of the inside walls,teeth of the stator core, on which the conductor segments are not leant,easily vibrates. As a result, magnetic noise increases due to anincrease in magnetic vibrations.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter and it isan object of the present invention to provide a rotary electric machinecapable of improving its power output in accordance with temperaturedecrease and reducing magnetic noise.

According to the present invention, a rotary electric machine includes arotor, a stator core disposed to oppose the rotor, and a stator windingwound around the stator core. The stator core is formed with a pluralityof slots extending in an axial direction. Each of the slots is definedwith a first wall and a second wall opposing each other in acircumferential direction. The stator winding includes insertionportions held in the slots. Each of the insertion portions has acircumferential width smaller than a distance between the first wall andthe second wall of the slot. The insertion portion is disposed to makecontact with one of the first wall and the second wall.

Since the width of the insertion portion is smaller than the distancebetween the first wall and the second wall of the slot, a gap is formedbetween the insertion portion and one of the first wall and the secondwall. Therefore, it is easy to insert the insertion portion in the slot.Further, since the insertion portion makes contact with one of the firstwall and the second wall, heat generated in the stator winding istransferred to the stator core. Therefore, temperature of the statorwinding decreases. Accordingly, power output of the rotary electricmachine improves. Also, vibrations of teeth reduce.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description made withreference to the accompanying drawings, in which like parts aredesignated by like reference numbers and in which:

FIG. 1 is a schematic view of a vehicular alternator, partly includes across-section, according to the embodiment of the present invention;

FIG. 2 is a cross-sectional view of a part of a stator core for showingarrangement of conductor segments held in slots according to theembodiment of the present invention;

FIG. 3 is a perspective view of the conductor segments constructing astator winding according to the embodiment of the present invention;

FIG. 4 is a perspective view of joining portions of the conductorsegments according to the embodiment of the present invention; and

FIG. 5 is a cross-sectional view of a part of the stator core forshowing arrangement of the conductor segments of a modified embodimentof the present invention.

DETAILED DESCRIPTION OF EMBODIMENT

The rotary electric machine of the present invention is for exampleapplied to a three-phase vehicular alternator that is mounted and fixedon an engine and driven by the engine. An embodiment of the vehicularalternator in which the present invention is applied will be describedin detail with reference to the drawings.

As shown in FIG. 1, the vehicular alternator 1 of the embodimentincludes a stator 2 functioning as an armature, a rotor 3 functioning asa field magnet, a housing 4 having a front housing 4 a and a rearhousing 4 b, and a rectifier 5. The front housing 4 a and the rearhousing 4 b hold the stator 2 by a stud bolt 4 c and rotatably supportthe rotor 3. The rectifier 5 rectifies an AC voltage output from thestator 2 to a DC voltage.

The rotor 3 rotates with a shaft 6. The rotor 3 includes a Lundell-typepole core 7, a field coil 8, slip rings 9, 10, a mixed flow fan 11, anda centrifugal fan 12 as air blowing devices. The shaft 6 is connected toa pulley 20 and rotated by an onboard engine (not shown) for driving avehicle.

The Lundell-type pole core 7 is constructed of a pair of pole cores. TheLundell-type pole core 7 includes a boss portion 71, which is fixed tothe shaft 6, disc portions 72, which extend from the ends of the bossportion 71 in a radial direction, and sixteen claw poles 73.

The mixed flow fan 11, which is adjacent to the pulley 20, includesblades that are arranged at acute angles and blades that are arranged atright angles to a base plate 111. The base plate 11 a is fixed to an endsurface of the pole core 7 such as by welding. The mixed flow fan 11rotates with the rotor 3. The centrifugal fan 12, which is further fromthe pulley 20 than the mixed flow fan 11, includes blades that arearranged at right angles to a base plate 121. The base plate 12 a isfixed to an end surface of the pole core 7 such as by welding.

A housing 4 forms air inlet holes 41 on its axial end surfaces. Also,the housing 4 forms cooling air outlet holes 42 on its shoulder portionscorresponding to the radially outer peripheries of a first coil ends 31a and a second coil ends 31 b of the stator 2.

The rectifier 5 is fixed to the end of the vehicular alternator 1 on aside opposite to the pulley 20. The first coil end 31 a is arranged tocorrespond to the rectifier 5.

The stator 2 includes a stator core 32, a stator winding 31, andinsulators 34. The stator winding 31 is constructed of a plurality ofelectric conductors held in slots formed on the stator core 32. Theinsulators 34 provide electrical insulation between the stator core 32and the stator winding 31. The stator core 32 is fixed by the stud bolt4 c after inserted in the front housing 4 a. The rear housing 4 b isplaced on the stator core 32 and fixed by a nut 4 d.

As shown in FIG. 2, the stator core 32 is formed with the plurality ofslots 35 in which the multi-phase stator winding 31 is held. In theembodiment, seventy-two slots 35, corresponding to the number of thepoles of the rotor 3, are arranged at regular intervals for holding thethree-phase stator winding 31.

The stator winding 31 can be grasped as a group of electric conductors.Even numbered electric conductors are held in each of the slots 35. Forexample, four electric conductors are held in each slot 35, as shown inFIG. 2.

The slot 35 extends in an axial direction of the stator core 32 a. Theelectric conductors are arranged parallel in the axial direction of thestator core 32. As shown in FIG. 2, the four electric conductors(insertion portions) are arranged in line in order of inner end layer,inner middle layer, outer middle layer, and outer end layer from theinner diameter side with respect to a radial direction of the statorcore 32.

Each of the electric conductors has a circumferential width (W1) that issmaller than a slot width (W2) of the slot 35, so that there is a gapbetween the electric conductor and an inside wall defining the slot 35when the electric conductor is inserted in the slot 35. Here, thecircumferential width (W1) of the electric conductor (insertion portion)is a dimension of the electric conductor in the circumferentialdirection of the stator core 32. The slot width (W2) is a distancebetween a first inside wall and a second inside wall defining the slot.The first inside wall and the second inside wall oppose in thecircumferential direction.

The electric conductors are connected in predetermined patterns, therebyconstructing the stator winding 31. First ends of the electricconductors are connected through continuous turn portions on a side ofthe first coil end 31 a and second ends of the electric conductors arejoined on a side of the second coil end 31 b.

One electric conductor in one slot, 35 pairs up with another electricconductor in another slot 35 that is a predetermined pole-pitch away.Specially, an electric conductor of a specific layer in the slot 35pairs up with an electric conductor of another layer in another slot 35that is a predetermined pole-pitch away, in order to maintain gapsbetween the plurality of electric conductors at the coil ends andarrange them orderly.

For example, an electric conductor 331 a of the inner end layer in thefirst slot 35 pairs up with an electric conductor 331 b of the outer endlayer in the second slot 35 that is one pole-pitch away in the clockwisedirection of the stator core 32. Likewise, an electric conductor 332 aof the inner middle layer in the first slot 35 pairs up with an electricconductor 332 b of the outer middle layer in the second slot 35 that isone pole-pitch away in the clockwise direction of the stator core 32.

The paired electric conductors 331 a, 331 b, and the paired electricconductors 332 a, 332 b are respectively connected through turn portions331 c, 332 c at one of the axial ends of the stator core 32. Therefore,the turn portion 332 c, which connects the electric conductor 332 b ofthe outer middle layer and the electric conductor 332 a of the innermiddle layer, is surrounded by the turn portion 331 c, which connectsthe electric conductor 331 b of the outer end layer and the electricconductor 331 a of the inner end layer, at one of the axial ends of thestator core 32.

A middle layer coil end is formed by connections of the electricconductors of the outer middle layers and the electric conductors of theinner middle layers. An outer layer coil end is formed by connections ofthe electric conductors of the outer end layers and the electricconductors of the inner end layers.

On the other hand, the electric conductor 332 a of the inner middlelayer in the first slot 35 also pairs up with an electric conductor 331a′ of the inner end layer in the second slot 35 that is one pole-pitchaway in the clockwise direction of the stator core 32. Likewise, anelectric conductor 331 b′ of the outer end layer in the first slot 35pairs up with the electric conductor 332 b of the outer middle layer inthe second slot 35. These electric conductors are connected together atthe opposite axial end of the stator core 32 by welding.

Therefore, at the opposite axial end of the stator core 32, a connectingportion of the electric conductor of the outer end layer and theelectric conductor of the outer middle layer and a connecting portion ofthe electric conductor of the inner end layer and the electric conductorof the inner middle layer are arranged in the radial direction of thestator core 32.

Adjacent layer coil ends are formed by connections of the electricconductors 331 b of the outer end layers and the electric conductors 332b of the outer middle layers and connections of the electric conductors331 a of the inner end layers and the electric conductors 332 a of theinner middle layers. In this way, at the opposite axial end of thestator core 32, the connecting portions of the paired electricconductors are arranged without overlapping.

The electric conductors are provided from U-shaped conductor segmentsthat are produced by forming electric wires into predetermined shapes.The electric wire has a constant thickness and substantiallyrectangular-shaped cross-sections. Thus, each of the electric conductorshas a first surface and a second surface. The first surface and thesecond surface are opposite to each other and face the first and thesecond inside walls of the slot 35, respectively.

As shown in FIG. 3, the electric conductor 331 a of the inner end layerand the electric conductor 331 b of the outer end layer are included ina large conductor segment 331. The electric conductor 332 a of the innermiddle layer and the electric conductor 332 b of the outer middle layerare included in a small segment 332. The large conductor segment 331 andthe small conductor segment 332 have substantially U-shape.

The large segment 331 and the small segment 332 are included in the baseconductor segments 33. The base conductor segments 33 are arrangedregularly in the slots 35 so that a coil that turns twice around thestator core 32 is constructed. However, the conductor segments thatinclude lead-out wires of the stator winding and turn portionsconnecting the first and the second laps are constructed of specialshape conductor segments, which are in different shape from the baseconductor segments 33.

In this embodiment, nine special shape conductor segments are provided.The connection between the first and the second laps is made by theconnection between the electric conductors of the end layer and themiddle layer. By this connection, special shape coil ends are formed.

In the large conductor segment 331, an inside distance between theelectric conductor (straight portion) 331 b of the outer end layer andthe electric conductor (straight portion) 331 a of the inner end layerof the large conductor segment 331 in the circumferential direction ofthe stator core 32 is slightly shorter than a central pitch P (FIG. 4)between central points of the first and second slots 35 in which theelectric conductor 331 b and 331 a are held, in the circumferentialdirection.

The inside distance between the pair of straight portions 331 b, 331 ais variable by resilient deformation of the turn portion 331 c. Thestraight portions 331 a, 331 b are inserted in the first slot and thesecond slot 35 while expanding the inside distance between the straightportions 331 b, 331 a. As a result, the electric conductors 331 b, 331 acontact the inside walls of the slots 35 on sides adjacent to the turnportions 331 c and are spaced from the opposite inside walls that are onthe sides opposite to the turn portions 331 c, by spring back of theresilient deformation.

In the small conductor segment 332, an inside distance between theelectric conductor 332 b of the outer middle layer and the electricconductor 332 a of the inner middle layer of the small conductor segment332 in the circumferential direction is slightly longer than the centralpitch P between the central points of the first and the second slots 35in which the electric conductors 332 b, 332 a are held.

The inside distance between the pair of straight portions 332 b, 332 ais variable by resilient deformation of the turn portion 332 c. Thestraight portions 332 a, 332 b are inserted in the first and secondslots 35 while decreasing the inside distance between the straightportions 332 b, 332 a. As a result, the straight portions 332 b, 332 aare held in the respective slots 35 such that the straight portions 332b, 332 a are in contact with the inside walls of the slots 35 that areon the sides opposite to the turn portion 331 c and spaced from theopposite inside walls of the slots 35 that are on the side adjacent tothe turn portion 332 c.

In this way, the large conductor segment 331 and the small conductorsegment 332 are held such that the straight portions 331 a, 331 b of thelarge conductor segment 331 are arranged to be close to each other andthe straight portions 332 a, 332 b of the small conductor segment 332are arranged to separate from each other, with respect to the centralpitch P.

Therefore, as shown in FIG. 2, in the slot 35, the straight portions ofthe large conductor segments 331 and the small conductor segment 332 arearranged in line in the radial direction of the stator core 32. Further,the straight portions are alternately in contact with the first insidewall and the second inside wall of the slot 35.

Next, a process of manufacturing the stator winding 31 will bedescribed. First, the base segments 33 are arranged such that the turnportion 332 c of the small conductor segment 332 is surrounded by theturn portion 331 c of the large conductor segment 331 and inserted inthe stator core 32 from one of the axial ends in the above-describedmanner.

Thus, the electric conductor 331 a, which is one of the straightportions of the large segment 331, is inserted in the inner end layer inthe first slot 35 of the stator core 32. The electric conductor 332 a,which is one of the straight portions of the small segment 332, isinserted in the inner middle layer 32 of the first slot 35. The electricconductor 331 b, which is the remaining straight portion of the largesegment 331, is inserted in the outer end layer of the second slot 35.The electric conductor 332 b, which is the remaining straight portion ofthe small segment 332, is inserted in the outer middle layer in thesecond slot 35.

As a result, the electric conductors 331 a, 332 a, 332 b′, 331 b′ arearranged in line in the slot 35 in this order from the inner end layerin the radial direction, as shown in FIG. 2. Here, the straight portions332 b′, 331 b′ are paired up with the electric conductors in a slot 35that is one-pole pitch away from the first slot.

After inserted, in the second coil end 31 b, joining portions 331 d, 331e of the electric conductors 331 a, 331 b of the end layers are tiltedfor one and a half slots in the direction that the large conductorsegment 331 opens. Joining portions 332 d, 332 e of the electricconductors 332 a, 332 b in the middle layers are tilted for one and ahalf slots in the direction that the small conductor segment 332 closes.

This step is repeated for all base conductor segments in the slots 35.Then, in the second coil end 31 b, the joining portion 331 e′ of theouter end layer and the joining portion 332 e of the outer middle layerare joined by welding, such as ultrasonic welding, arc welding andbrazing, and by other method, to have electrical continuity. The joiningportion 332 d of the inner middle layer and the joining portion 331 d ofthe inner end layer are joined in the similar manner. In this way, thestator 2 shown in FIG. 4 is produced.

In the vehicular alternator 1 of the embodiment, since thecircumferential width (W1) of the electric conductors (insertionportions) is smaller than the slot width (W2), the gap is formed betweenthe electric conductor and one of the first inside wall and the secondinside wall of the slot 35. Therefore, it is easy to insert theconductor segments 33 in the slots 35. With this, workability improves.

Also, since the electric conductor is in contact with one of the firstinside wall and the second inside wall of the slot 35, heat of thestator winding 31 is effectively transferred to the inside wall of theslot 35. Therefore, temperature of the stator winding 31 decreases,resulting in an improvement of power output.

The electric conductor of the conductor segment 33 has substantially arectangular-shaped cross-section to correspond to the shape of the slot35. Therefore, contact surface area between the inside wall of the slot35 and the electric conductor increases, so the efficiency of heattransfer improves. Also, the electric conductor is less likely tovibrate. As a result, magnetic noise of the stator winding 31 reduces.

In the slot 35, a plurality of electric conductors is arranged in linein the radial direction. Further, the electric conductors alternatelycontact the first inside wall and the second inside wall of the slot.Therefore, the electric conductors make contacts with the inside wallsof the slots equally. With this, heat of the stator winding 31 isuniformly transferred to the inside walls of the slots. Further, it ispossible to equally limit the teeth of the stator core 32 fromvibrating.

Further, the electric conductors are in contact with the inside walls ofthe slots 35 by the spring back of the turn portions 331 c, 332 c of theconductor segments 33. Therefore, it is not required to add specificparts and process to make the electric conductors contact the insidewalls of the slots 35. Accordingly, the power output improvement inaccordance with the temperature decrease and the reduction of magneticnoise are achieved with the simple structure.

Further, forming the stator winding with the conductor segments easilyincreases thickness of the stator winding. With this, it is possible tofurther decrease the temperature in accordance with a decrease inresistance. Also, power output further improves and magnetic noisefurther reduces in accordance with an increase in rigidity.

In the above embodiment, four electric conductors are held in each slot35. Instead, eight electric conductors can be arranged in line in theradial direction in the slot 35, for example. As shown in FIG. 5, theeight electric conductors are alternately in contact with the firstinside wall and the second inside wall of the slot 35.

In the above-described embodiment, the stator winding 31 is constructedby using the U-shaped conductor segments. The present invention can beemployed to a stator winding that is constructed by substantiallystraight conductor segments without having turn portions and by acontinuous wire.

The present invention can be employed to various kinds of rotaryelectric machines, such as other kinds of generators or motors otherthan the generators.

The present invention should not be limited to the disclosedembodiments, but may be implemented in other ways without departing fromthe spirit of the invention.

1. A rotary electric machine, comprising: a rotor; a stator coredisposed to oppose the rotor, wherein the stator core is formed with aplurality of slots extending in an axial direction, and each of theslots is defined with a first wall and a second wall that oppose eachother in a circumferential direction; and a stator winding wound aroundthe stator core, wherein the stator winding is a continuous winding,wherein the stator winding includes insertion portions held in theslots, wherein each of the insertion portions has a cirumferential widththat is smaller than a distance between the first wall and the secondwall of the slot, wherein one of the insertion portions contacts thefirst wall of the slot through an insulator, wherein another one of theinsertion portions contacts the second wall of the slot through theinsulator.
 2. The rotary electric machine according to claim 1, whereinan even number of insertion portions is inserted into each slot, whereinhalf of the insertion portions contact the first wall of the slot, andthe remaining half of the insertion portions contact the second wall ofthe slot.
 3. The rotary electric machine according to claim 1, whereinthe insertion portions alternatively contact the first wall and thesecond wall.
 4. The rotary electric machine according to claim 1,wherein the insertion portions contact the walls of the slot through theinsulator by coil spring back.
 5. The rotary electric machine accordingto claim 2, wherein the insertion portions contact the walls of the slotthrough the insulator by coil spring back.
 6. The rotary electricmachine according to claim 3, wherein the insertion portions contact thewalls of the slot through the insulator by coil spring back.